Terpene derivative



containing elements such as oxygen,

Patented Mar. 2, 1943 Joseph N.-Borgiin, Wilmington, Hercules Powder Company,

DeL. "amt. Wilmington, Del,

a corporation of Delaware No Drawing. Application April 9, 1941,

' Serial No. 887,874

19 Claims. (Cl. 28H!!!) This invention relates to new terpene compounds and a method for their formation. More particularly, it relates to new hydroxyl-containing terpene esters and to a method for their preparation.

In accordance with this invention an unsaturated terpene is brought into intimate contact with oxygen and with an organic carboxylic acid and reacted therewith until a hydroxyl-containing terpene ester is formed. This reaction may be conducted under pressure if desired, and it may be facilitated by the aid of catalysts if desired. By the reaction in accordance with this invention, there is formed a mixture of oily waterinsoluble hydroxyl-containing terpene esters and water-soluble hydroxyl-containing terpene esters. Both products are characterized by ester linkages and by hydroxyl groups upon secondary and tertiary carbon atoms of the terpenic portion of the molecule. The two types of product mentioned may be separated and recovered from the reaction mixture.

The terpene utilized in the method according to this invention will be an unsaturated terpene which may be of a substituted or unsubstituted nature. Thus, the term "terpene" as used herein and in the claims is used in its broader sense, and includes both terpene hydrocarbons and derivatives thereof which may be considered as terpene hydrocarbons which have been modified by substitution or addition thereto of elements or groups sulphur, nitrogen, halogens, and so forth. Suitable unsaturated terpenes which may be utilized are such unsaturated terpene hydrocarbons as, for example, alpha-pinene, beta-pinene, dipentene, terpinene, terpinolene, allo-ocimene, alpha-pyronene, beta-pyronene, myrcene, pheliandrene. fenchene, the various unsaturated sesquiterpenes, polvterpenes and the like; such unsaturated terpene alcohols as alpha -terpineol,beta-terpineol, terpinenol, and the like; such unsaturated terpene esters as alpha-terpinyl acetate, alpha-terpinyl formate, beta-terpinyl acetate, beta-terpinyl formate, terpinenol propionate, and the like; such unsaturated terpene ethers as terpinyl methyl ether, terpinyl ethyl ether, terpinyl glycol ether, and the like; terpinyl mercaptan; terpinyl amine; terpinyl chloride; and so forth.

Suitable organic carboxylic acids in the process according to this invention are, for example, such aliphatic acids as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, capriilic acid, glycolic acid, tartaric acid, lactic acid, citric acid, malic acid, succinic acid, maleic acid, nitropropionic acid, furoic acid, tetrahydrofuroic acid; such cycloaliphatic acids as the naphthenic acids and such aromatic acids as benzoic acid, cumic, salicyclic acid, phthalic acid, terephthalic acid, and the like.

The oxygen utilized in the reaction according to this invention may be provided in the tom of "any gas containing free oxygen. Pure oxygenmay be utilized, if desired. However, oxygen is most conveniently provided in the ordinary at-, mospheric form.

The reaction in accordance with this invention. is brought about by mixing the terpene and the carboxylic acid utilized and bringing this mixture into intimate contact with oxygen. This may be accomplished by vigorous agitation of the liquid reactants to provide a constant renewal of surface exposed to the oxygen. Preferably, air or oxygen is whipped up into the liquid or is bubbled through the liquid reactants. The reaction is facilitated by providing the oxygen under superatmospheric pressure. Thus, air at any convenient pressure may supply the oxygen, the speed of the reaction greatly increasing as the pressure is increased. Pressures up to several thousand atmospheres may be utilized. the actual pressure being dictated largely by convenience.

The reaction may be conducted at any temperature in the range between about 0 C. and about 150 0., and preferably the temperature will be maintained between about 20' C. and about 50 C. External cooling may be provided to control the temperature at the desired level since the reaction is exothermic.

The time required to form hydroxyl-containing terpene esters by the method in accordance with this invention varies considerably with the reactants and with the conditions of reaction utilized. The conditions of oxygen contact largely determine the minimum time of reaction for a given set of reactants. Where the liquid reactants are merely agitated in air, or where air is slowly bubbled through a large mass of liquid reactants, the reaction time will usually be long and may be from about 8 hours to in excess of 3 weeks. In most cases, substantial completion of the reaction will be attained within a period from about 8 hours to about 150 hours under atmospheric pressure. At superatmospheric pressure, i. e., at high oxygen pressures, the reaction be substantially completed inin most cases will from about 4 to about 20 hours.

Usually, the reaction mixture will consist es.- se'ntially of the terpene and the carboxylic acid reacted with the acid in excess of that expected to enter into the reaction. However, inert diluents such as benzene, toluene, acetone, methylethyl ketone, ethyl acetate, petroleum ether and the like may be present if desired.

The oxidation etherification process in accordance with this invention may be conducted under substantially anhydrous conditions, or it may be conducted in the presence of water. Reaction in' the presence of water is preferred where a maximum yield of water-soluble products is desired.

In general, the effect of water is to increase the ratio of hydroxyl groups to ester groups in the product and to increase the water-solubility of the products. The quantity of water may vary widely according to the type of product desired, and may be as much as ten times the weight of the terpene utilized. It will be appreciated that the ratio of hydroxyl groups to ester groups depends to some extent upon the ratio of water to carboxylic acid in the reaction mixture. Usually, the concentration of the acid on the basis of the water present will be above about 2%.

The reaction may b facilitated if desired by the use of catalysts. Oxidation or oxygen carrier catalysts which operate by reason of active surfaces such as activated carbon, flake aluminum, activated alumina, iron powder, and the like: which contain elements which readily undergo reversible changes .in valence such as, for example, potassium permanganate, selenium oxide, cerium sulphate, vanadium sulphate, cobalt naphthanate, manganese linoleate, lead naphthanate, lead linoleate, lead mercaptides, and the like; or hydrohalides of basic nitrogen compounds (ammonia and amines), for example, ammonium chloride, ammonium bromide, aniline hydrochloride, pyridine hydrochloride, triethanolamine, hydrochloride, methylamine hydrochloride, and the like are effective. Such catalysts may be utilized under any of the conditions of reaction previously mentioned. The quantity of catalyst utilized may be varied widely. However, a quantity between about 0.1% and about by weight of the terpene present is usually ample. I

The reaction in accordance with this invention will usually be conducted until substantially no more oxygen is absorbed by the reacting mixture. Operation may be by batches or, where the conditions bring about rapid reaction, operation may be continuous. The reaction product will be a mixture containing hydroxy terpene esters of an oily nature insoluble in water and hydroxy terpene esters of a water-soluble nature.

. These products may be recovered from the reaction mixture by adding water thereto if little or none is present, and separating the water layer and the oily layer which form;

- The recovery of the water-soluble products is best accomplished by evaporation of the water mm the water layer at a high vacuum and relatively low temperatures. Where the carboxylic acid utilized is volatile, excess thereof will evaporate with the water. Non-volatile acids may be removed by extraction with water-immiscible solvents such as ethyl acetate, ether, propyl acetate, benzene, and the like prior to this evaporation step. Upon evaporation of the water and any volatile associated materials, and removal of excess acids, a neutral syrup which is believed to be a mixture of several hydroxy terpene esters is obtained. when this syrup is allowed to stand over a period of some days, a crystalline hydroxy ester will usually form and separate out. The separation of the crystalline product is reatly facilitated by seeding. It occurs most readily when the carboxylic acid used is a lower aliphatic acid (1. e., six or less carbonatoms), especially a lower fatty acid. Both crystalline and non-crystalline products usually have a slight odor suggestive of caramel. They are colorless to a light 70 amber and have a somewhat bitter taste.

Water-insoluble hydroxy esters are recovered by removing volatile materials from the oily layer a under vacuum, the hydroxy esters remaining as the least volatile material. Non-volatile acids 75 present may be removed by extraction with mild aqueous alkali such as a dilute sodium carbonate solution. The product is a light neutral oily material when excess acid reactant has been elliciently removed.

The water-soluble product and the water-insoluble product obtained by the method in accordance with this invention are terpene esters of the carboxylic acid utilized having a hydroxyl upon the terpenic portion of the molecules. It is a characteristic of the compounds that they contain a hydroxyl upon a tertiary carbon atom of the terpenic structure, and in addition in the case of the water-soluble compounds, they will usually contain a hydroxyl upon a secondary carbon atom of the terpenic structure. The watersolubl product in general has a higher hydroxyl content than the water-insoluble product.

The products in accordance with this invention may be modified by heating in the presence of a strong, inorganic acid, such as. sulphuric acid, sodium acid sulphate, phosphoric acid, nitric acid, hydrochloric acid, etc.; or in the presence of dehydrating surface active agents such as activated silica gel, activated alumina, and the like, whereupon products of reduced hydroxyl content are obtained by chemical dehydration. Thus, the water-soluble hydroxy esters may be dehydrated to water-insoluble hydroxy esters or dehydrated further to more unsaturated esters having no hydroxy groups.

' Both types of products are believed to consist of a mixture of rather similar compounds which differ from each other in part by degree of oxida-- tion and esteriilcation and in part by isomerization. It is believed that the addition of hydroxyl groups and ester groups is not entirely uniform, so that several isomers may be, obtained from the same I terpenes. The exact mechanism of the reaction according to this invention is not known. The reactions involve increase in molecular weight of the terpene, and are, therefore, of the nature of addition reactions. Unlike more drastic oxidation procedures, no appreciable scission or cracking of the terpene takes place, although isomerization and/or decyclicization of the terpenic structure may occur. It is believed the following equations express the nature of the reactions, for example, when a terpene hydrocarbon is reacted with oxygen and acetic acid:

The process and product in accordance with this invention are illustrated by specific embodiments thereof in the following examples.

Example 1 A mixture consisting of 2000 milliliters of terpinolene, 750 milliliters of water, 25 milliliters of acetic acid, and 2 grams of sodium lauryl sulphate (as a wetting agent to improve contact) was agitated for 194 hours while a slow stream of air was bubbled therethrough. The mixture rose in temperature from an initial 25 C. to 46 C. and gradually dropped in temperature. At the end of this period an additional 100 milliliters of water were added and the reaction continued for an additional 90 hours. Twenty-five milliliters of acetic acid and 200 milliliters of water were then added and the reaction conducted for 135 hours. The resulting reaction mixture was then permitted to separate into layers, and an oily layer of 1275 milliliters and an aqueous layer of 1760 milliliters were drawn ofi. It will be noted that the aqueous portion increased 760 milliliters, while the oily layer decreased 725 milliliters as a result of the reaction which took place. The aqueous layer was evaporated under vacuum over a steam bath and a yield of 1133 grams of substantially neutral water-soluble product was obtained. This product shows the following properties upon analysis:

Saponification number 76 d 15.6/15.6 1.1006 Secondary alcohol analysis per cent 5.3 Tertiary alcohol analysis do 477 Fraction Fraction No. 1 No. 2 Rwdu Yield Per cent. 27. 5 l7. 7 47. 5 Saponitication number 22. 5 7. 5 20 d l5.6/l5.6 8645 8661 9719 Secondary alcohol. Per t. 0.5 3.0 11. Tertiary alcohol d 27. 5 l7. 7 47. 5

The analyses indicate the presence of appreciable quantities of tertiary and secondary alcohols, partially acetylated.

Example 2 A mixture consisting of 2000 milliliters of a terpinolene cut (boiling range, 185 C. to 195 C.) obtained by processing of pine wood, 750 milliliters of water, and 25 milliliters of acetic acid was agitated while a slow stream of air was passed therethrough. The temperature rosebe noted that the aqueous layer had increased 835 milliliters, while the oily layer had decreased 1090 milliliters.

The aqueous layers was evaporated under reduced pressure and at a temperature of about 60 C. to obtain 1106 grams of substantially neutral syrupy water-soluble product. This product had the following analysis:

Saponification number '63 d 156/156 1.102 Secondary alcohol analysis ..per cent 11.0 Tertiary alcohol analysis do.. 295

Thewater-soluble product was permitted to stand for .two weeks at room temperature, to form a white crystalline product. The crystals were removed by filtration, 218 grams of crystals being obtained from 940 grams of the water-soluble product. The crystals obtained had the following properties:

Melting point .l30-135 C. Sign of double refraction 2 V 30-40 Indices of refraction:

Low Ca .1.505 High Ca .1.57-1;59

Orientation of optic plane Incl.ined about 35 from predominant face; parallel to long direction of crystal.

Crystal habit l 6-sided crystals. Terminal angle Parallel extinction.

The oily layer obtained was fractionated by distillation at a pressure of about 60 mm. at a bath temperature of 100 C. In this manner two distillation fractions and a distillation residue having the following characteristics were obtained:

of secondary and tertiary alcohols partially acetylated.

Example 3 A mixture consisting of 500 milliliters of a ter pinolene cut (boiling range, C. to C.) obtained from pine wood, 500 milliliters of water, and 50 milliliters'of formic acid was agitated for 150 hours While a slow stream of air was passed therethrough. The temperature rose from an initial 25 C. to 45C. and dropped slowly thereafter. The resulting reaction mixture was permitted to separate into two layers. A water layer of 630 milliliters and an oily layer of 430 milliliters were recovered by decantation. Evaporation of the water layer under a high vacuum resulted in a yield of 57 grams of water-soluble syrupy product consisting of partial formates of terpene polyhydric alcohols.

Example 4 A mixture consisting of 1000 milliliters of a terpene cut obtained from pine wood (boiling range. 5-.95% at 179-191 C.; d 15.6/15.6, 0.8622), 1000 milliliters of acetic acid, and 7 grams of activated carbon was agitated 90 hours at a temperature varying between 22 C. and 35 C. while a. slow stream of air was. passed there'- through. The resulting reaction product was then filtered to remove the activated carbon utilized as catalyst. Separation of water-soluble and water-insoluble products was then achieved Acid number 54.7 Saponification number 212.5 Ester number 157.8

Hydroxyl value (Zerewitinofi) per cent 12.8

It will be noted that free acid remained in this product as analyzed. This product consisted largely of terpene hydroxy acetates.

Example 5 A mixture consisting of 500 n lliliters of propionic acid, 500 milliliters of a erpinolene cut (boiling range from 185 C. to 35 C.) and 3.5 grams of activated carbon was agitated 90 hours at a temperature varying between 25 and 32 C. while a slow stream of air was passed therethrough. The resulting mass was filtered to remove the activated carbon utilized as catalyst, and the filtrate was then diluted with 800 milliliters of water. The two layers forming were separated by decantation. The aqueous layer was evaporated under vacuum at a temperature of about 70 C. to obtain 121 grams of watersoluble product which analyzed as follows:

Saponification number 281 1W 1.4790 Hydroxyl (Zerewitinofi) per cent 14.4

This product consisted essentially of terpene hydroxy propionates. It crystallized partially on standing for one month.

The oily layerwas steam distilled to obtain 235 milliliters of distillate and 122 grams of residue. The distillate consisted in considerable proportion of readily volatile terpenes and excess propionic acid, the residue representing hydroxy esters. This residue analyzed as follows:

Saponification number 153.7 1W 1.5014 Hydroxyl (Zerewitinofi) per cent 10.9

The product consisted largely of terpene hydroxy propionates which, however, were not as highly substituted as those of the water-soluble product.

Example 6 temperature 0145-60 C. gave a yield of 29 grams of water-soluble terpene hydroxy formates.

Example 7 A mixture consisting of 500 milliliters of allo-ocimene, 500 milliliters of water, 100 milliliters of acetic acid, and 0.2 grams of flake aluminum was agitated for 90 hours at a temperature varying between 20 C. and 35 C., while a slow stream of air was passed therethrough. At the end of the reaction period, the aluminum used as a catalyst was removed by filtration, and the filtrate permitted to form two layers. An aqueous layer of 650 milliliters and an oily layer of 365 milliliters were obtained by decantation. The aqueous layer was then evaporated under vacuum at a temperature of 60'l0 C. to obtain a yield of 125 grams of water-soluble hydroxy acetates derived from the allo-ocimene.

Example 8 was evaporated at'an absolute pressure of about 3 centimeters. In this manner 156 grams of water-soluble hydroxylated terpene lactic acid ester were obtained.

Example 9 A mixture consisting of 500 milliliters of mixed alphaand beta-pyronenes, 50 grams of oxalic acid and 600 milliliters of water was thoroughly agitated for a period of '72 hours in contact with air under a pressure of 1500 lbs. /sq. inch at temperatures within the range of 30-45 C. At the end of this period, two layers were permitted to separate. The aqueous layer was titrated with calcium acetate to precipitate free oxalic acid, and the calcium oxalate which formed was removed by filtration. The resulting aqueous solution was evaporated at an absolute pressure of 3 centimeters to leave a yield of 123 grams of water-soluble hydroxylated terpene oxalate ester.

Example 10 A mixture consisting of 500 milliliters of myrcene, 400 milliliters of acetic-acid, 100 milliliters of water and 5 grams of activated carbon was thoroughly agitated for a period of hours in contact with air at 1400 lbs./sq. inch pressure at a temperature maintained within the range be tween 35 and 45 C. At the end of this period, 400 milliliters of water were stirred into the reaction mixture after which two layers were per- I mitted to form. The aqueous layer was evaporated at an absolute pressure of 2.5 centimeters to yield 143 grams of water-soluble hydroxylated terpene esters.

The products in accordance with this invention are useful'in the flotation of minerals and as coupling solvents for water-soluble and water-insoluble materials. The water-insoluble materials are excellent-slowly evaporating solvents for cellulose derivative lacquers and for varnishes.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

What I claim and desire to protect by Letters Patent is:

1. A method which comprises subjecting a mixture comprising an unsaturated terpene and an organic carboxylic acid to reaction with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

2. A method which comprises subjecting a mixture comprising an unsaturated terpene hydrocarbon and an organic carboxylic acid to re.- action with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

3. A method which comprises subjecting a mixture comprising an unsaturated terpene hydrocarbon and an organic carboxylic acid to reaction with oxygen in the gaseous free form at a temperature between about C. and about 150 C. until a freely water-soluble hydroxylated terpene ester is formed, and recovering the said ester from the reaction mixture.

4. A method which comprises subjecting a mixture comprising allo-ocimene and an organic carboxylic acid to reaction with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

5. A method which comprises subjecting a mixture comprising myrcene and an organic carboxylic acid to reaction with a gas containing free oxygen as the only reactive ingredient imtil a hydroxylated terpene ester is produced.

6. A method which comprises subjecting a mixture comprising a pyronene and an organic carboxylic acid to reaction with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

7. A method which comprises reacting a mixture containing an unsaturated terpene and an organic carboxylic acid with free oxygen, the free oxygen being contained in a gas under superatmospheric pressure until a hydroxylated terpene ester is produced.

8. A method which comprises subjecting a mixture comprising an unsaturated terpene, an organic carboxylic acid, and an oxidation catalyst to reaction with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

9. A method which comprises subjecting a mixture comprising an unsaturated terpene, an organic carboxylic 'acid,.and an oxidation catalyst to reaction with a gas containing free oxygen as the only reactive ingredient until a water-soluble hydroxylated terpene ester is produced. and recovering the water-soluble terpene hydroxy ester.

10. A method which comprises subjecting a mixture comprising an unsaturated terpene, an organic carboxylic acid, and water to reaction with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

11. A method which comprises subjecting a mixture comprising an unsaturated terpene hydrocarbon, an organic carboxylic acid. and water to reaction with a gas containing free oxygen as the only reactive ingredient until a water-soluble hydroxylated terpene ester is produced, and recovering the said water-soluble compound.

12. A method which comprises subjecting a mixture comprising an unsaturated terpene hydrocarbon and an organic carboxylic acid to reaction with free oxygen under superatmospheric pressure in the presence of an oxidation catalyst until a hydroxylated terpene ester is produced.

13. A method which comprises subjecting a mixture comprising an unsaturated terpene hydrocarbon, an organic carboxylic acid, and water to reaction with air under superatmospheric pressure in the presence of an oxidation catalyst until a water-soluble hydroxylated terpene ester is produced, and recovering the said water-soluble hydroxylated terpene ester.

14. A method which comprises subjecting a mixture comprising an unsaturated terpene and an aliphatic carboxylic acid to reaction with a gas containing free oxygen as the only reactive ingredient until a hydroxylated terpene ester is produced.

15. A method which comprises subjecting a mixture comprising an unsaturated terpene and a lower fatty acid to reaction with a gas containing free oxygen as the only reactive ingredient until a. hydroxylated terpene ester is produced.

16. Water-soluble hydroxylated carboxylic acid terpene esters characterized by at least one tertiary terpene hydroxy], by the property of losing hydroxy] on heating with-sulfuric acid, and by being capable oiconcentration to a syrup which upon standing deposits colorless crystals of terpene hydroxy ester, said hydroxylated terpene esters being prepared by the method defined in claim 1.

17. Water-soluble hydroxylated formic acid terpene esters characterized by at least one tertiary terpene hydroxyl, by the property oi losing hydroxyl on heating with sulfuric acid, and by being capable of concentration to a syrup which upon standing deposits colorless crystals of terpene hydroxy ester, said hydroxylated terpene esters being formed by reacting an unsaturated terpene and formic acid according to the process of claim 1.

18. Water-soluble hydroxylated acetic acid I terpene esters characterized by at least one tertiary terpene hydroxy], by the property of losing hydroxyl on heating with sulfuric acid, and by being capable of concentration to a syrup which upon standing deposits colorless crystals of terpene hydroxy ester, said hydroxylated terpene esters being formed by reacting an unsaturated terpene and acetic acid according to the process of claim 1.

19. Water-soluble hydroxylated propionic acid terpene esters characterized by at least one tertiary terpene hydroxy], by the property of losing hydroxy] on heating with sulfuric acid. and by being capable of concentration to a syrup which upon standing deposits colorless crystals of terpene hydroxy ester, said hydroxylated terpene esters being formed by reacting an unsaturated terpene and propionic acid according to the proces of claim 1.

JOSEPH N. BORGLIN. 

